Changes in precipitation extremes over the “Three-River Headwaters” region, hinterland of the Tibetan Plateau, during 1960–2012

Based on daily precipitation from 12 meteorological stations over hinterland of the Tibetan Plateau observed by the China Meteorological Administration in 1960–2012, changes in ten selected indices of precipitation extremes are investigated. The results demonstrate that very wet day precipitation, extremely wet day precipitation, simple daily intensity index, wet day precipitation, heavy precipitation days, and heavier precipitation days over the “Three-River Headwaters” region exhibit increasing trends during the study period, with wet day precipitation statistically significant. However, non-significant decreasing trends are found for other indices, including maximum 1-day precipitation, maximum 5-day precipitation, and consecutive wet days with exception of consecutive dry days. Additionally, the stations with significant variations are mainly distributed over the northern “Three-River Headwaters” region. Additionally, abrupt changes in non-significant increasing trend for R95p and R99p are observed in 2007 and 2006, respectively, and major periodic variations with periods of a 6-year and a 20-year occurring in the extreme precipitation. The contribution of extreme precipitation to total precipitation has non-significant increase in the research region. Changes in small scale atmospheric circulation indicate that the main part of the moisture over the study area is from the Indian Ocean via southwesterly wind during the summer monsoon period.